(440a) Manage Water Quality at ABU-Rawash WWTP, Egypt

The Abu-Rawash wastewater treatment plant (WWTP) is one of the largest WWTPs in Egypt. The last extension allows the plant to handle an average flow of 1.20 million m³/day. This plant receives daily about 1,450,000 m³ of raw wastewater. Because the volume of sewage coming to the plant exceeds the capacity of the plant, which provides only primary treatment, more than 250,000 m³ of excess sewage is discharged daily directly to the Rosetta branch of the Nile River without even primary treatment. This research investigated a process to improve the Abu-Rawash WWTP effluent water quality with the application of aluminum chloride (AlCl₃) at lower pH values. Secondary (biological) treatment units will be constructed to improve effluent quality in order to meet water quality standards specified in Egyptian law 48/1982. The secondary treatment units at the Abu-Rawash WWTP are expected to begin operation in ten years. The chemical treatment can be applied for 10 years until the biological treatment units at the Abu-Rawash WWTP begin working. The grit removal chambers and the primary sedimentation tanks are connected by a canal that splits into two branches in order to distribute wastewater to the primary sedimentation tanks. The proposed solution can be applied to a single branch in order compare the existing situation and the proposed solution. The coagulant and carbon dioxide units can be installed directly after the grit removal chamber. Ten concrete barriers will be installed downstream of the coagulant and carbon dioxide units to destabilize very fine suspended solids and colloidal particles in an effort to enhance the agglomeration of the destabilized particles. A static mixer can also be used instead of the concrete barriers to enhance the mixing between the wastewater and coagulant. Complete mixing between the wastewater and coagulant will occur near the center part of the primary sedimentation tank. The total cost of implementing the proposed scenario is ~ $2.25 million, which includes the cost of the coagulant unit, concrete barriers or static mixers, a carbon dioxide unit, and the pH controller, as well as the chemical costs of aluminum chloride and carbon dioxide.